"Smelly" compound as viable material for bioplastic production

A hydrocarbon compound present in stool and certain flowering plants, although at lower concentrations can be used for bioplastic production, researchers find.

Polyethylene furanoate (PEF), which contains the hydrocarbon, furan that can be derived from maize, wood and certain types of grain is garnering attention as a viable and renewable material alternative to oil-based plastic. PEF, which is widely used in packaging, is found to be superior to standard polyethylene terephthalate (PET) in protecting against oxygen, carbon dioxide and water; thus giving products enclosed in plastic greater durability.

The success of PEF made researchers at Sweden’s Lund University interested in other renewable materials that could potentially be used for plastic production. Chemical engineering doctoral student Ping Wang has produced a plastic based on indole, a heavier hydrocarbon molecule than furan, that is present in human faeces and smells accordingly. The compound is also found in lower concentrations in certain flowering plants and has a more agreeable aroma. This effect, according to the researchers is due to our sense of smell decoding the aroma differently depending on the amount and combination.

The research team is thought to be the only one researching indole polyesters, and their results are promising. A regular PET bottle’s glass-liquid transition temperature – when the material softens and deforms – is 70°C. The most successful PEF experiments withstand about 86°C. However, one of Wang’s indole plastics is stable up to 99°C.

“These are preliminary results, but we have seen that polyester plastic has better mechanical properties, which makes it more sustainable. This can lead to better recycling in the future. At present, PET bottles can only be recycled once, then they must be used for something else such as textiles”, says associate professor Baozhong Zhang, who is supervising the research team.

Currently, indole is only produced on a small scale and used mainly in perfumes and drugs. It may be possible to use bioengineering methods to produce indole from sugar through fermentation. However, such a process would first need to be analysed more thoroughly before the production cost can be calculated.

Wang is continuing her research by examining the indole plastic’s potential in other application areas.